PROJECT SUMMARY ? TILTON PROJECT One of the most difficult challenges for environmental health is to evaluate hazards from exposure to chemical mixtures. The environmental health science community recognizes a growing need to evaluate toxicity for structurally diverse PAHs and their transformation and breakdown products in complex mixtures, using human-relevant and metabolically competent research models. This Biomedical Science Research Project will assess the toxicity of PAHs in complex mixtures associated with Superfund sites in a 3D human lung model composed of primary human bronchial epithelial cells (HBEC) differentiated at the air-liquid interface. We will quantify the toxicity of PAHs and PAH mixtures targeting lungs via endpoints relevant for multiple exposure routes (inhalation, diet, dermal). We will rely on benchmark dose modeling to identify a threshold response for comparison. We will apply integrated RNAseq and functional proteomics to identify mechanisms by which PAHs exert adverse health outcomes in exposed populations and to identify susceptible individuals in those populations. The overall goal of this project is to understand how individual PAHs contribute to toxicity in mixtures and to establish a relationship between chemical exposure and toxicity. We will apply the outcomes of these studies to assess and communicate human health risk and to evaluate susceptibility for relevant populations. We propose to achieve these aims: 1) quantify the toxicity of PAHs and PAH mixtures in the 3D lung model, 2) assess the role of metabolism on the toxicity of individual PAHs in the 3D human lung model and 3) elucidate the mechanisms of PAH toxicity in the 3D human lung model.